1. Field of the Invention
The invention relates to semiconductor devices exhibiting quantum mechanical performance characteristics, and in particular it relates to such semiconductor devices used as current sources.
2. Description of the Prior Art
Conventional semiconductor circuitry, even ultra miniaturized circuits, usually operate in a mode that can be described by classical or nonquantum mechanical, electrical theories of solids. However, in some cases the operation of the device cannot be explained by such classical theories, but only through a quantum mechanical theory. One such device is a Josephson Junction which operates to produce a quantized voltage in terms of e/h, where e is the charge of an electron and h Planck's constant. Additionally quantum behavior in quantum Hall effect devices is also observed and can be utilized to provide a quantized resistance which is a multiple of h/e.sup.2.
Quantized adiabatic particle transport has been predicted and described by D. J. Thouless in Physical Review B 27,6083 (1983). According to Thouless an integral number of electrons is transported through any cross section as long as the Fermi gap in the conducting material is open at all times. Thouless has theoretically demonstrated that if the potential in a semiconductor is changed slowly in such a way that it returns to its starting value, the current across a boundary will be quantized for filled bands in an infinitely periodic system, but not in a finite torus. Thouless, however, did not propose any particular device in which quantization of current could be utilized or applied for any practical purpose.
Therefore, what is needed is an apparatus and method for providing quantized current as predicted by theory which would allow control of the quantized current to be known and made usefully available.